1. Field of the Invention
The invention relates to an apparatus for positioning a sample carrier plate.
The invention further relates to a method for positioning a sample carrier plate.
2. Description of the Related Art
The microtiter plate has been established as standard for the simultaneous processing of a large number of small sample volumes in molecular biology. This comprises a rectangular plate of fixed dimensions, which contains a defined number of isolated cavities (wells) in rows and columns. Inside these wells different samples can be tested for their properties independently of one another. Microtiter plates having 96, 384, or 1536 wells are usually widely used in pharmaceutical, chemical, and biological research.
With increasing degree of automation and the increase in the number of wells in a microtiter plate, there is a tendency to automate filling processes and other processes. Various types of pipetting heads are known for simultaneously filling the wells, which heads can accommodate a number of pipetting tips corresponding to the number of wells.
The greater the number of wells of the corresponding microtiter plate, the smaller the diameter of each of these indentations. The requirements on the positioning accuracy of microtiter plate to pipetting head therefore increase. Furthermore, in a large number of application in pharmaceutical, chemical, and biological research it is necessary to ensure thorough mixing of the components in the wells of the microtiter plate. A simple possibility for influencing the local concentration and therefore the probability of interaction of the reaction partners is an external energy input by defined movement (shaking) of the reaction container. The advantage of such a method is the freedom from contamination as a result of the noncontact energy input (in contrast to methods using moving mixing tools). Furthermore, due to this mixing movement of a shaking apparatus, the homogenization of the temperature within the sample is also accelerated with respect to the compensating processes naturally present.
Manufacturing tolerances in the production of microtiter plates in length, width, and base height act directly on the positioning of the microtiter plate since the microtiter plate is conventionally frequently displaced by springs toward solid obstacles.
In case of conventional systems positioning pieces are often firmly attached for fixing microfilter plates during the process of pipetting and shaking. It is the object of the positioning pieces to always hold the microtiter plate in position. Springs can be contained in these positioning pieces. However, the spring force produced should be so great that the microtiter plate is held in position against the centrifugal force produced by the orbital mixing movement. Due to the high force required, the insertion of the microtiter plates into the shaking apparatus by the transporting apparatus (for example, gripper arm) of a robot can possibly be difficult or impossible. It is therefore problematical to fundamentally dispense with resilient elements since a clearance is then required in the receiving area as a result of the mentioned manufacturing tolerances (for example, ±0.5 mm), which in an unfavorable case can be 1 mm. Such a clearance allows undesirable movements of the microtiter plate during the shaking process and also conflicts with the aim of a precise positioning of the microtiter plate, in particular in the case of microtiter plates having 1536 wells, whose diameter for example is around 1 mm.
EP 1,186,891 discloses that in order to enable the spatial alignment of a support plate, this has a joint head on the underside which lies in a joint socket of a support plate. A connector of the joint head is guided through a central opening of the joint socket, which bears a clamping ring abutting against the outer side of the joint socket, which can be pressed by means of a tensile slip for fixing the alignment of the support plate. Two diagonally outwardly displaceable centering stops located opposite one another in a mirror-inverted manner on the upper side of the support plate are fastened to diagonally displaceable sliders. These engage at the opposite ends of a rotatable coupling lever with the same. This lever sits on a vertical shaft, which extends from the underside of the support plate through a hole in the joint head as far as the end of the connector. There said lever carries an actuating lever which can be rotated against the restoring force of a spiral spring for movement of the centering stops outward to allow a lowering or lifting of a microtiter plate.
WO 86/07232 discloses an apparatus for positioning a circuit panel.
EP 1,111,391 discloses a device for holding an item, in particular a microtiter plate, comprising a laying surface, where a stop limiting the displacement of the item on one side in the plane of the same is provided in the area of the laying surface, as well as a clamping apparatus having a clamping part that can be retracted with respect to the stop against a pretension.
DE 10 2004 021 664 discloses a microtiter plate shaking apparatus comprising a vibratory plate which has a reception zone for the microtiter plate and positioning pieces disposed thereon for the microtiter plate to be held. At least one positioning piece is movably mounted and can be moved between a working position and a release position. The at least one movably mounted positioning piece is movable from the working into the release position by means of a drive.
WO 99/13339 discloses a positioning apparatus for positioning a microtiter plate. A positioning platform can be provided in a surrounding platform. A further platform can be provided in the positioning platform. The surrounding platform has actuators. A movable carrier platform of the positioning platform can be moved relative to the carrier platform. In this case, bulk-like elements are disposed along the longitudinal side between the innermost further platform and the surrounded positioning platform. By means of a fluid such as compressed air, for example, the bulk-like elements can absorb fluid or blow out fluid so that a movement and positioning of the inner surrounded platform can thereby be implemented.
It is still difficult to position a sample receiving container precisely on a substrate.